Logarithmic RMS and Linear Envelope Detector for RF Power
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power detectors in wireless communication systems struggle to accurately measure the average power level and input voltage envelope of complex modulated RF signals, especially with high-crest factor signals, leading to inefficiencies in power amplifiers and limited dynamic range in detecting low power levels.
Innovation Solution
A power detector system that includes a logarithmic RMS detector and a linear envelope detector, with a gain or attenuation element to shift the operating range of the envelope detector, allowing for precise detection of average power and voltage envelope, and utilizing a series of gain or attenuation stages to progressively amplify or attenuate the RF input signal for improved dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional power detectors using diode detection or successive amplification are used, then the device complexity is reduced, but the measurement precision deteriorates due to intolerable errors in measuring signal power
Solution Approach 1:
The detector is divided into multiple independent detection channels: a logarithmic RMS detection channel for measuring average power and a linear envelope detection channel for measuring peak envelope power. Each channel uses detection circuits optimized for its specific measurement function, allowing high precision measurements without requiring a single complex detector design.
Solution Approach 2:
A variable gain amplifier is introduced as an intermediary component between the RF input and the detection channels. This amplifier dynamically adjusts the signal level based on the detected envelope, enabling the detector to accurately measure both low and high power levels by adapting the input signal amplitude to the optimal range of the detection circuits.
2Use of energy by moving object
If the transmitter operates at full power to handle peak signal levels, then the power efficiency is improved, but the linearity requirements cannot be met for high-crest factor signals
Solution Approach 1:
The detector provides feedback information about both the average power level (via logarithmic RMS detection) and the peak envelope power (via linear envelope detection). This dual feedback enables the transmitter to dynamically adjust its operating point, maintaining signal linearity by ensuring peak power handling capability while optimizing average power efficiency through informed back-off operation.
Solution Approach 2:
The transmitter operates in a dynamic manner by continuously monitoring the detected envelope levels and adjusting the power amplifier operating point in real-time. This allows the system to operate at high efficiency for average power while maintaining linearity for peak signals, rather than being constrained to a fixed operating point.
3Use of energy by moving object
If a variable power supply is utilized in envelope tracking system, then the power efficiency is improved, but the device complexity increases due to need for precise envelope detection
Solution Approach 1:
The envelope detection function is segmented into a dedicated linear envelope detection channel that is separate from the average power measurement channel. This dedicated channel uses simplified circuitry optimized specifically for envelope detection, reducing the complexity burden on the overall system while providing the precise envelope information needed for efficient variable power supply control.
4Measurement precision
If long integration times are used for accurate RMS calculation, then the measurement precision is improved, but the response speed deteriorates and envelope level cannot be provided
Solution Approach 1:
The detection system is segmented into two parallel channels: a logarithmic RMS detection channel that uses long integration times for accurate average power measurement, and a linear envelope detection channel that uses short integration times for fast envelope level measurement. This segmentation allows both precise power measurement and rapid envelope tracking to occur simultaneously without interfering with each other.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides accurate measurement of RF power across a wide dynamic range, enabling efficient power management and reducing errors in low power level detection, with the logarithmic RMS detector offering linear-in-dB characteristics and the envelope detector achieving a wider operational range through selective amplification or attenuation.
Implementation Method 1
The logarithmic RMS detector receives an RF input signal and detects the average power level of the RF input signal
Implementation Method 2
The linear envelope detector receives the amplified or attenuated version of the RF input signal and detects the voltage envelope of the RF input signal
Implementation Method 3
The gain or attenuation element also receives the RF input signal and generates an amplified or attenuated version of the RF input signal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed herein are power detectors and methods for detecting the average power level of an RF input signal and the voltage envelope of the RF input signal. Also disclosed herein are linear envelope detectors and methods for detecting the voltage envelope of an RF input signal.